Various types of contact test apparatus have been proposed; in one such apparatus, a contact element, typically a small wheel, is lowered on a surface of the sample terminal, the contact resistance of which is to be tested. To lower the test contact on the sample terminal, it has been proposed to drive an eccenter disk or a cam disk from an electric motor, in which a cam follower periodically is lifted off to likewise raise the test contact from the sample terminal, and then again to permit contacting the test contact on the test terminal at a different position. Such an apparatus is described, for example, in the journal "Metalloberflache", year 32 (1978), issue 10, ("Metal Surfaces", article entitled "Testing of Contact Conditions of Galvanically Deposited Layers (I)", by K. L. Schiff and R. Schnabl). The test apparatus permits automatic test cycles with controllable contact force, controlled positioning of the test contact and prevention of stray deposition of corrosion products by the test contact.
Test apparatus of this type require above all precise and gentle positioning of the test contact on the surface to be tested or measured, that is, on the sample terminal. In order to provide for such positioning, the engagement speed of the test contact has been made adjustable, for example by utilizing a hydraulically, pneumatically or electro-dynamically operated scale system. The positioning speed of the test contact on the sample terminal could not readily be controlled in eccenter disk systems of the scale arrangement. Oscillations and vibrations during positioning of the movable test contact thus could be transferred onto the surface of the sample terminal.